In eighteen seventy-six, inside a third floor walk-up garret apartment in the Scollay Square section of Boston Mass., only a short distance from the sight of the first battle of the revolutionary war, Alexander Graham Bell spoke the first words transmitted over telephone wires. Bell's transmission of sound over telephone wires initiated a revolution in communications whose scope rivals that of the political revolution initiated by the sound, heard nearby, of “the shot heard round the world.”
Technical innovations have dramatically transformed the telecommunications industry in the ensuing years. For example, telecommunications switching systems have evolved considerably from “hand operated” systems in which one instrument was electrically connected (through a hierarchical switching network) to another with the intervention of a human operator who would physically plug one circuit into another. Such direct electrical connection of two or more channels between two points (at least one channel in each direction), a connection that provides a user with exclusive use of the channels to exchange information, is referred to as circuit switching, or line switching. Human operators have largely been replaced by systems which employ electronic switching systems (ESS, e.g., 5ESS), in which the instruments are automatically connected through the network by electronic systems. Nevertheless, such switching systems often still employ circuit switching, a technique which yields highly reliable service, particularly for such “real time” communications applications as voice, in which the momentary loss of a channel is annoying, and repeated such losses are unacceptable.
Not only has switching technology undergone major changes, the type of traffic being carried on telephone lines has also changed dramatically. Although originally designed for voice traffic and “tuned” to operation in the voice band between approximately 350 and 4000 Hz, the telecommunications infrastructure also carries data, through the use of various channels, or tones. However, with the growing use of the Internet, and the potential development such high bandwidth applications such as interactive distance-learning and video on demand, the existing telecommunications infrastructure is in danger of being overwhelmed. A large portion of the system's transmission medium has been replaced with high speed trunks which employ fiber optic transmission media, microwave media, and line of sight optical media, for example, to meet the ever mounting demand for high speed data transmission capability. Data traffic is increasing at a rate of approximately 300% per year, while voice traffic is only increasing at the relatively slow rate of approximately 5% per year. However, a huge installed base of transmission media, switching devices, and other telecommunications infrastructure provide the telecommunications path for the vast majority of telecommunications providers and users.
Various quality of service categories are supported by ATM and their varied requirements exacerbate the difficulty of modeling an ATM compatible switching system. Consequently, many conventional ATM systems either employ conservative systems modeling, which results in underutilized facilities such as bandwidth and/or buffers, or aggressive modeling, which degrade system performance.
A system and method that enable the efficient combination and management of circuit-switched and packet-switched facilities, thereby taking advantage of the tremendous installed base of equipment and facilities while, at the same time, permitting an extensive upgrade of data facilities, which typically employ packet switching systems, would therefore be highly desirable.